US4653698A - Safety system for coal pulverizers - Google Patents
Safety system for coal pulverizers Download PDFInfo
- Publication number
- US4653698A US4653698A US06/899,765 US89976586A US4653698A US 4653698 A US4653698 A US 4653698A US 89976586 A US89976586 A US 89976586A US 4653698 A US4653698 A US 4653698A
- Authority
- US
- United States
- Prior art keywords
- signal
- coal pulverizer
- comparing
- inerting
- pulverizer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C23/00—Auxiliary methods or auxiliary devices or accessories specially adapted for crushing or disintegrating not provided for in preceding groups or not specially adapted to apparatus covered by a single preceding group
- B02C23/04—Safety devices
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K1/00—Preparation of lump or pulverulent fuel in readiness for delivery to combustion apparatus
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K2201/00—Pretreatment of solid fuel
- F23K2201/10—Pulverizing
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S241/00—Solid material comminution or disintegration
- Y10S241/14—Grinding in inert, controlled atmosphere
Definitions
- the present invention generally relates to control systems for coal pulverizers and particularly to safety control systems for detecting and controlling hazardous conditions in a coal pulverizer.
- pulverized-coal systems pulverize coal, deliver it to the fuel-burning equipment, and accomplish complete combustion in the furnace with a minimum of excess air.
- the system operates as a continuous process and, within specified design limitations, the coal supply or feed can be varied as rapidly and as widely as required by the combustion process.
- a small portion of the air required for combustion (15 to 20% in current installations) is used to transport the coal to the burner. This is known as primary air.
- primary air In the direct-firing system, primary air is also used to dry the coal in the pulverizer.
- the remainder of the combustion air (80 to 85%) is introduced at the burner and is known as secondary air.
- Spontaneous combustion of coal is dependent on a sufficient supply of oxygen to maintain the reaction and on the surface area exposed.
- Coals with a high surface area, due to small particle size, as in pulverized coal fuel, are particularly liable to self heating. This problem is of special significance to the safe operation and performance of industrial coal pulverizers.
- Spontaneous combustion may result in deterioration in the quality of the coal, in damage to the power plant, and in certain cases, for example, where critical concentrations of coal dust are involved, may provide the ignition source for an explosion.
- thermocouples to measure the rise in outlet temperature of the pulverizing mill or infrared gas analyzers to detect the buildup of CO produced in the mill.
- thermocouples or RTD's are normally part of the control system for mill operation. However, they are a relatively insensitive means for detecting pulverizer fires. At best, they warn of impending trouble only a few minutes before it actually occurs, and in some cases, do not even detect a significant temperature rise before a fire or explosion is evident.
- the ineffectiveness of thermocouples and RTD's in this application is due, in part, to the shielding used to protect them from the corrosive coal particles. Shields reduce heat conduction, slowing response time.
- Infrared gas analyzers are used to compare the CO content of the incoming and outgoing mill air and in effect, the amount of CO produced in the mill.
- infrared gas analyzers require extensive filtering and dehydration of the gas sample extracted from the mill, to prevent interference by water vapor and particulate matter. Due to the high cost and maintenance requirements of infrared absorption analyzers, it is the usual practice to use one analyzer for several measurement points. Continuous measurement of each mill is not provided, thus, slowing response time. Nevertheless, this provides an improvement over the thermocuple and RTD method described.
- the invention described herein overcomes the stated problems of prior art safety systems and provides an improvement over the existing art. It is not dependent on the measurement of mill outlet temperature, the removal of moisture and all particulate matter from the sample extracted from the mill or multi-point sampling.
- the invention incorporates the use of a standard single point oxygen and CO analyzer directly mounted to the coal pulverizing mill providing a continuous percent by volume measurement of oxygen content and a continuous measurement of CO gas concentration of the mill atmosphere.
- the O 2 portion of the analyzer uses a sensor operating at a temperature where any combustible volatile material will combine with O 2 in the sample. The sensor will then respond to the free or uncombined O 2 remaining.
- the resulting measurement denoted net or residual, O 2
- O 2 The resulting measurement, denoted net or residual, O 2
- An additional significant indicator of a potentially hazardous condition is, thus, provided, augmenting the CO measurement.
- the combined measurement of CO and net O 2 concentration in the mill atmosphere is used to indicate and alarm both the onset and progress of spontaneous combustion within the mill.
- one aspect of the present invention is to provide an automated system capable of being integrated into a plant's pulverizer management and combustion control system designed to monitor the performance of and detect impending fires and explosions in industrial coal pulverizers and alarm such conditions.
- Another aspect of the present invention is to provide an automated alarm system based on a net oxygen measurement in the coal pulverizer.
- Yet another aspect of the present invention is to provide an automated alarm system based on a predetermined carbon monoxide rise per time.
- Still yet another aspect of the present invention is to provide an automated inerting control of the coal pulverizer upon detection of either a predetermined net oxygen level or an absolute carbon monoxide level.
- FIG. 1 is a schematic drawing of the safety control system of the present invention.
- FIG. 2 is a schematic of the monitoring and control logic of the FIG. 1 safety control system.
- the invention described herein is a reliable, relatively low-cost automated safety system 8 capable of being integrated into a plant's computer control system designed to monitor the performance of and detect impending fires and explosions in electric-utility and industrial coal pulverizers by monitoring the level of carbon monoxide (CO) and net oxygen (O 2 ) concentration in a pulverized coal mill atmosphere.
- CO carbon monoxide
- O 2 net oxygen
- the combined measurement of CO and O 2 concentration in the mill atmosphere is used to indicate the oxidation rate of the coal to preclude spontaneous combustion. Additionally, the measurement of net O 2 concentration, when combined with other measurements may provide the basis for overall mill performance calculations and the quality of the pulverized coal.
- the CO/O 2 sample probe 10 is typically placed in a coal pulverizer 12 classifier outlet zone.
- a sample of gas is drawn through the probe 10 which has a porous high temperature filter 14.
- the filter 14 is required to maintain trouble-free operation by minimizing the amount of particulate matter drawn into the analyzer.
- a suitable filter 14 for this application is of a type described in U.S. Pat. No. 4,286,472.
- the air sample drawn from the coal pulverizer 12 is then analyzed for percent by volume of oxygen (O 2 ) content and CO gas concentration in ppm (parts per million) via a known oxygen and CO gas analyzer 16 designed to operate in a harsh power plant environment and having autocalibration capabilities.
- a suitable analyzer for this application is one manufactured by the Bailey Controls Company of Babcock and Wilcox and is known as the Type OL Oxygen and CO Analyzer.
- This analyzer 16 has a CO range of 0-1000 ppm and an O 2 range of 0.1-25%. Electrical signals corresponding to carbon monoxide and oxygen concentrations are respectively transmitted to a monitoring system control 18 located in the central control room along lines 20 and 22.
- CO and O 2 concentrations are displayed and/or recorded on a strip-chart recorder 24.
- net O 2 levels represent typically 16% O 2 and normal CO levels range between 40 and 80 ppm. If the net O 2 concentration falls below a certain predetermined level, typically 15% and/or the amount of CO produced exceeds a predetermined rise level considered cause for concern, typically a 50 ppm/minute sudden rise, the system 8 activates audible and visible alarms 26, 28 to alert the operator who in turn may manually take corrective action to inert the pulverizer 12 or permit the automatic monitoring system 8 to continue until it initiates an automatic inert to bring the pulverizer 12 operating parameters under control.
- the monitoring and control logic assembly 18 utilizes both a net oxygen measurement provided by the analyzer 16 along line 20 as well as a carbon monoxide measurement provided along line 22 from analyzer 16. To, on the one hand. actuate alarms 26 and 28 at predetermined levels of net oxygen and predetermined rise times of carbon mcnoxide concentration. Also, when the net oxygen levels and the absolute carbon monoxide levels exceed certain critical limits, automatic inerting of the pulverizer 12 is accomplished by controllably opening a valve 30 which allows some inerting media such as carbon dioxide or steam to flow along a line 32 into the pulverizer 12.
- the net oxygen measurement from line 20 is transmitted along a line 34 to a difference station 36 having a setpoint set at a predetermined net oxygen control point transmitted along line 38.
- the difference station 36 compares the actual net oxygen measurement provided by the analyzer 16 representing the net oxygen level in the pulverizer 12 and compares it with the setpoint oxygen level which, in the present situation, is set at 15%.
- the present setpoint of 15% is based on the assumption that the typical atmosphere in the pulverizer representative of normal conditions is approximately 16% and the initial alarm condition is desired to be a warning indicative of potential problem areas.
- the difference station 36 thus compares the two signals and provides an error signal along line 40 which is one input of an AND gate 42.
- the other input of the AND gate 42 is provided by a constant negative signal from a predetermined source along line 44.
- a positive level error signal will be transmitted along line 40 to the AND gate 42 which then will fail to provide any control signal along line 46, failing to actuate the alarm 26.
- the output along line 40 becomes negative and in combination with the constant negative signal along line 44, will result in a conduction of the AND gate 42, causing a control signal to be transmitted along line 46 to the alarm 26 to thus actuate it and provide an indication of potential problems in the pulverizer 12 atmosphere.
- the measured carbon monoxide signal transmitted along line 22 may also provide an actuation of the alternate alarm 28.
- the measured carbon monoxide signal is transmitted to a derivative action controller 48 which will be sensitive to any variations in the carbon monoxide level and will effectively provide an output signal along line 50 indicative of the slope or rate of change of the carbon monoxide level in the pulverizing mill 12.
- the output of the derivative action controller 48 is transmitted to a difference station 52 having a predetermined setpoint along line 54 indicative of a rate of carbon monoxide change which would indicate coal ignition in the pulverizer 12. Such a rate of change is typically taken to be a 50 ppm/minute rate of carbon monoxide change.
- the output of the difference station 52 is transmitted along the line 56 to an AND gate 58 having a second input of a constant negative value provided along line 60.
- the rate of carbon monoxide change normally stays below the 50 ppm/minute setpoint resulting in a negative output signal from the difference station 52.
- the signal transmitted along line 56 turns positive, causing the AND gate 58 to start conducting a control signal along line 62 to the alarm 28 actuating the alarm 28 to indicate a potentially hazardous atmosphere in the pulverizer 12.
- Automatic inerting of the pulverizer 12 is actuated by a difference station 64 which has a setpoint provided to it along line 66 having a net oxygen level significantly lower than the setpoint level provided to difference station 36.
- the difference station 64 has a net oxygen setpoint of 9%.
- the net oxygen level measured and transmitted to the difference station 64 will exceed the 9% setpoint and the error signal produced by the difference station 64 will be a positive level signal transmitted along line 68 to an AND gate 70.
- the other input of the AND gate 70 is provided by a constant negative level signal transmitted to the AND gate 70 along line 72.
- the inputs to the AND gate 70 will be positive and negative, providing no control signal from the output of the AND gate along line 74.
- the output of the difference station 64 turns negative, providing two negative inputs to the AND gate 70 and resulting in a control signal along line 74 being transmitted to a switching circuit 76.
- the switching circuit 76 is a normally open circuit, preventing the signal transmitted from a controller 78 from reaching the control valve 30.
- the switching circuit 76 changes to a closed-circuit condition, turning over control of the valve 30 to the controller 78.
- the controller 78 has an input signal indicative of the actual net oxygen level in the pulverizer 12 which is provided by a parallel line 80, paralleling the net oxygen signal in line 20.
- the setpoint of the controller is provided along line 82 from some predetermined setpoint station and is typically set at a 12% level.
- the controller 78 will open valve 30, causing an inerting atmosphere, such as carbon dioxide, to be delivered to the pulverizer 12 until a somewhat normal ambient is reached close to the setpoint level of 12%.
- the reason for keeping the setpoint of the controller 78 at a somewhat lower than typically normal atmosphere is to minimize the shock to the pulverizer 12 due to the inerting process.
- the switching circuit is then switched back to its normally open condition by a reset signal provided along line 84 from either a manual source or an automatic source which can be tied to some parameter indicative of the reestablishment of normal ambient conditions in the pulverizer 12.
- the actuation of the automatic inerting means is also alternatively done upon the sensing of a predetermined absolute level of carbon monoxide in the pulverizer 12.
- the carbon monoxide signal normally provided along line 22 is tapped by a line 86 to provide one input of a difference station 88.
- the setpoint of the difference station 88 is provided along line 90 from a predetermined setpoint station typically set at an absolute carbon monoxide level of 200 ppm.
- a positive error signal will be transmitted by the difference station 88 along line 92 to an AND gate 94.
- the other input to AND gate 94 is provided by a line 96 connected to a constant negative level source.
- opposite polarity signals are provided to the AND gate 94, preventing the establishment of any control signal along line 98 from the AND gate 94.
- the error signal transmitted to the AND gate 94 turns negative, causing the conduction of the AND gate 94 and the establishment of a control signal along line 98 to the switching circuit 76.
- this causes the switching circuit 76 to become conductive, turning control of the valve 30 over to the controller 78.
- automatic inerting of the pulverizer 12 occurs until a reset signal is established along line 84, causing the switching circuit 76 to again become non-conductive and causing the valve 30 to switch its normally closed position.
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Disintegrating Or Milling (AREA)
Abstract
Description
Claims (6)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/899,765 US4653698A (en) | 1983-08-01 | 1986-08-22 | Safety system for coal pulverizers |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US51935283A | 1983-08-01 | 1983-08-01 | |
US06/899,765 US4653698A (en) | 1983-08-01 | 1986-08-22 | Safety system for coal pulverizers |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US06751479 Continuation | 1985-07-03 |
Publications (1)
Publication Number | Publication Date |
---|---|
US4653698A true US4653698A (en) | 1987-03-31 |
Family
ID=27059804
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US06/899,765 Expired - Fee Related US4653698A (en) | 1983-08-01 | 1986-08-22 | Safety system for coal pulverizers |
Country Status (1)
Country | Link |
---|---|
US (1) | US4653698A (en) |
Cited By (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4778113A (en) * | 1986-04-29 | 1988-10-18 | The Babcock & Wilcox Company | Apparatus for monitoring low level combustibles |
US4817441A (en) * | 1988-05-02 | 1989-04-04 | O'donnell & Associates, Inc. | Process and apparatus for obtaining a gas sample |
US4846410A (en) * | 1986-04-26 | 1989-07-11 | The Babcock & Wilcox Company | Apparatus for monitoring low-level combustibles |
US5611494A (en) * | 1995-06-30 | 1997-03-18 | Williams; Robert M. | Isolated intelligent and interrelated control system with manual substitution |
CN102884377A (en) * | 2010-05-14 | 2013-01-16 | 株式会社神户制钢所 | Method for preventing ignition and device for preventing ignition in pulverizer |
CN102893090A (en) * | 2010-05-17 | 2013-01-23 | 株式会社神户制钢所 | Ignition prevention method and ignition prevention apparatus for crusher |
CN103432696A (en) * | 2013-09-04 | 2013-12-11 | 鞍钢集团矿业公司 | Telescopic spray fire extinguishing system used for material feeding part of coal mill |
US9421551B2 (en) | 2012-05-01 | 2016-08-23 | Innovative Combustion Technologies, Inc. | Pulverizer mill protection system |
US9494319B2 (en) | 2013-03-15 | 2016-11-15 | General Electric Technology Gmbh | Pulverizer monitoring |
US9604226B2 (en) | 2012-05-01 | 2017-03-28 | Innovative Combustion Technologies, Inc. | Pulverizer mill protection system |
US10520249B2 (en) | 2016-01-22 | 2019-12-31 | Encana Corporation | Process and apparatus for processing a hydrocarbon gas stream |
CN111790509A (en) * | 2020-06-09 | 2020-10-20 | 内蒙古岱海发电有限责任公司 | Coal mill outlet pulverized coal pipe fireproof monitoring system and control method thereof |
US20220164499A1 (en) * | 2020-11-17 | 2022-05-26 | Northwestern Polytechnical University | Method and system for determining transportation safety of pulverized coal |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3477650A (en) * | 1967-11-28 | 1969-11-11 | Williams Patent Crusher & Pulv | Apparatus to provide inert atmosphere in material reducing mills |
US3909954A (en) * | 1974-04-03 | 1975-10-07 | Marc K Zoukourian | Device for prevention and protection against fire and explosion in the lines of the treatment of inflammable comminuted products |
GB1485448A (en) * | 1974-11-11 | 1977-09-14 | Boc International Ltd | Comminuting combustible material |
US4226371A (en) * | 1979-04-06 | 1980-10-07 | Willams Robert M | Inert grinding and direct firing in coal burning systems |
US4244529A (en) * | 1979-05-07 | 1981-01-13 | The Cleveland Cliffs Iron Company | Inerting of pulverizing mills for combustible materials |
-
1986
- 1986-08-22 US US06/899,765 patent/US4653698A/en not_active Expired - Fee Related
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3477650A (en) * | 1967-11-28 | 1969-11-11 | Williams Patent Crusher & Pulv | Apparatus to provide inert atmosphere in material reducing mills |
US3909954A (en) * | 1974-04-03 | 1975-10-07 | Marc K Zoukourian | Device for prevention and protection against fire and explosion in the lines of the treatment of inflammable comminuted products |
GB1485448A (en) * | 1974-11-11 | 1977-09-14 | Boc International Ltd | Comminuting combustible material |
US4226371A (en) * | 1979-04-06 | 1980-10-07 | Willams Robert M | Inert grinding and direct firing in coal burning systems |
US4244529A (en) * | 1979-05-07 | 1981-01-13 | The Cleveland Cliffs Iron Company | Inerting of pulverizing mills for combustible materials |
Cited By (17)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4846410A (en) * | 1986-04-26 | 1989-07-11 | The Babcock & Wilcox Company | Apparatus for monitoring low-level combustibles |
US4778113A (en) * | 1986-04-29 | 1988-10-18 | The Babcock & Wilcox Company | Apparatus for monitoring low level combustibles |
US4817441A (en) * | 1988-05-02 | 1989-04-04 | O'donnell & Associates, Inc. | Process and apparatus for obtaining a gas sample |
US5611494A (en) * | 1995-06-30 | 1997-03-18 | Williams; Robert M. | Isolated intelligent and interrelated control system with manual substitution |
CN102884377B (en) * | 2010-05-14 | 2016-04-27 | 株式会社神户制钢所 | The prevention method on fire of pulverizer and anti-locking apparatus on fire |
CN102884377A (en) * | 2010-05-14 | 2013-01-16 | 株式会社神户制钢所 | Method for preventing ignition and device for preventing ignition in pulverizer |
CN102893090A (en) * | 2010-05-17 | 2013-01-23 | 株式会社神户制钢所 | Ignition prevention method and ignition prevention apparatus for crusher |
CN102893090B (en) * | 2010-05-17 | 2015-04-15 | 株式会社神户制钢所 | Ignition prevention method and ignition prevention apparatus for crusher |
US9604226B2 (en) | 2012-05-01 | 2017-03-28 | Innovative Combustion Technologies, Inc. | Pulverizer mill protection system |
US9421551B2 (en) | 2012-05-01 | 2016-08-23 | Innovative Combustion Technologies, Inc. | Pulverizer mill protection system |
US9494319B2 (en) | 2013-03-15 | 2016-11-15 | General Electric Technology Gmbh | Pulverizer monitoring |
CN103432696B (en) * | 2013-09-04 | 2015-07-01 | 鞍钢集团矿业公司 | Telescopic spray fire extinguishing system used for material feeding part of coal mill |
CN103432696A (en) * | 2013-09-04 | 2013-12-11 | 鞍钢集团矿业公司 | Telescopic spray fire extinguishing system used for material feeding part of coal mill |
US10520249B2 (en) | 2016-01-22 | 2019-12-31 | Encana Corporation | Process and apparatus for processing a hydrocarbon gas stream |
CN111790509A (en) * | 2020-06-09 | 2020-10-20 | 内蒙古岱海发电有限责任公司 | Coal mill outlet pulverized coal pipe fireproof monitoring system and control method thereof |
US20220164499A1 (en) * | 2020-11-17 | 2022-05-26 | Northwestern Polytechnical University | Method and system for determining transportation safety of pulverized coal |
US12019961B2 (en) * | 2020-11-17 | 2024-06-25 | Northwestern Polytechnical University | Method and system for determining transportation safety of pulverized coal |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP0132974B2 (en) | Safety systems for coal pulverizers | |
US4653698A (en) | Safety system for coal pulverizers | |
US4846410A (en) | Apparatus for monitoring low-level combustibles | |
EP0244074B1 (en) | Safety systems for coal pulverizing mills | |
EP0305446B1 (en) | Coal pulverizer inerting and fire extinguishing system | |
US4778113A (en) | Apparatus for monitoring low level combustibles | |
US3867640A (en) | Dust sampling system | |
CA1205544A (en) | Method for monitoring furnace installations | |
GB2114778A (en) | Methods of and apparatus for controlling the residual oxygen content of waste gases of blower- type firing installations | |
US3557725A (en) | Furnace emission control system | |
US4099165A (en) | Fire detection apparatus in a preheater | |
EP0314133B1 (en) | Oil cooled fluid compression apparatus | |
KR0116821Y1 (en) | Fire prevention system of powdered coal manufacture plant | |
Zalosh | Review of coal pulverizer fire and explosion incidents | |
Toro et al. | Controls for burning solid wastes | |
JPH06304495A (en) | Monitor for state of dust in hopper of electric dust collector | |
JPS5823300B2 (en) | Safety devices in flammable powder transportation equipment | |
White | Detecting pulverizer fes before they start | |
JPH04165208A (en) | Burner | |
JPH0333003Y2 (en) | ||
CS210949B1 (en) | Method of indication of fuel supply interruption into fluid fireplace and equipment for execution of the method | |
JP2022173153A (en) | Method of monitoring operation of gas burner system, and gas burner system | |
JPH0226188B2 (en) | ||
Alameddin | Industrial coal-fired explosion hazards | |
JPH0238857B2 (en) |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: BABCOCK & WILCOX TRACY POWER, INC., A CORP. OF DE, Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:BABCOCK & WILCOX COMPANY, THE, A CORP. OF DE;REEL/FRAME:005161/0198 Effective date: 19890831 |
|
AS | Assignment |
Owner name: ELSAG INTERNATIONAL B.V., A CORP. OF THE NETHERLAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:BABCOCK & WILCOX TRACY POWER, INC., A CORP. OF DE;REEL/FRAME:005238/0432 Effective date: 19891031 |
|
FPAY | Fee payment |
Year of fee payment: 4 |
|
FEPP | Fee payment procedure |
Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
FPAY | Fee payment |
Year of fee payment: 8 |
|
FEPP | Fee payment procedure |
Free format text: PAYER NUMBER DE-ASSIGNED (ORIGINAL EVENT CODE: RMPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
REMI | Maintenance fee reminder mailed | ||
LAPS | Lapse for failure to pay maintenance fees | ||
FP | Lapsed due to failure to pay maintenance fee |
Effective date: 19990331 |
|
STCH | Information on status: patent discontinuation |
Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 |